Sight for dive bombing



June 11 1946. i M. E. BROWDER ET AL 2,401,744

7 SIGHT FOR DIVE BOMBING Filed June 21, 1935 2 Sheets-Sheet l Emma:

'dlbe'nb weflhewcer June 11, 1946. M. E. BROWDER ET AL 2,401,744

' SIGHT FOR DIVE BOMBING Filed June 21, 1935 2 Sheets-Sheet 2 TWO AMPLlF/ERS .Egyensizns:

- JHLEL'Browder awe werfizezlmer by I Patented June 11, 1946 SIGHT FORDIVE EOIVEEING Maurice E. Browder, United States Navy, and AlbertWertheimer, Washington, D. C.

Application June 21, 1935, Serial No. 27,798

(Granted under the act of March 3, 1883, as amended April 39, 1928; 3'700. G. 757) 13 Ciaims.

This invention relates to bomb sights used in dive bombing. It is theobject thereof to provide a sight which will continuously generate thecorrect line of sight to the target irrespective of the maneuvering ofthe bomber.

In the drawings:

Figs. 1 and 2 show diagrammatically the relations existing among theseveral factors involved in dropping the bomb during the dive;

, Fig. 3 illustrates an elementary form of a device embodying theprinciples of our invention.

Fig. 4 shows one embodiment of our invention;

Fig. 5 is a plan view of the coils in the gyroscopic follow-up system.

Fig. 6 illustrates schematically a gyroscopic control usable with ourinvention; and

As long as bombing is done at low altitudes in very steep dives, evenpoint blank aiming may result in some hits on the target. However, asthe art of defense against dive bombing progresses, higher altitudesmust be used and it becomes necessary to have some sort of sightingdevice to make the bombing successful.

In Fig. 1 the line OH is horizontal, the line OO represents the altitudeof the line OH above the ground, the line OP represents the axis of adiving plane and. the line OT is the line of sight from point 0 to thetarget T. (In the discussion of this figure it is assumed that theflight path and the axis of the plane coincide.) If the plane is at thealtitude 00' at the instant the bomb is released, then the distance OTis the horizontal distance traveled by the bomb during its fall and theline OT is the line of sight. The distance OT depends on the speed ofthe plane, on the altitude, and on the angle of dive. In order that thebomb shall strike the target T the angle. between the vertical and theline of si ht must be equal to arctangent OT/OO, which is not the sameas the angle of dive. Thus the line of sight must be inclined at acertain angle to the axis of the plane and it is the function of ourinvention to generate this angle correctly for all conditions of speed,altitude, and dive angle.

Actually, when a plane is diving, the flight path does not coincide withthe axis of the plane, and this must be taken into account in computingthe line of sight with reference to the axis of the plane. In Fig. 2 areshown the factors that must be considered and as represented therein:

00' is the altitude at release of the bomb;

CT is the horizontal distance passed over by the bomb during its fall;

OS is the flight path, that is, the line actually followed by the plane;

OP is the axis of the diving plane;

OT is the line of sight to the target;

I) is the dive angle, that is, the angle between the vertical and theflight path;

0 is the lift angle, that is, the angle betweeen the plane and theflight path.

13 is the sight angle, that is, the angle between the line of sight andthe axis of the plane; and,

A is the angle oi inclination, that is, the angle between the axis ofthe plane and the vertical.

Let the speed of the plane along the flight path be denoted by V and thealtitude by Y.

If the effects of air resistance are neglected, the sight angle for adrop in vacuo is given by:

sight angle in accordance with (1) or (2), it

' would necessarily be extremely complicated and entirely impracticablefor use in a plane intended for dive bombing.

After actual computations of the sight angle from (2) for the range ofthe variables of practical importance, it was found that the results ofsuch computations could be expressed with sufiicient precision by anempirical formula of the form:

(3) (BL) =K(AL) where L is the lift angle for a vertical dive and isconstant for any type of plane, while K is a factor which depends onlyon the speed and altitude, is constant for any given set of conditions,and is independent of the other variables. All angles are vectorsreckoned positively from the axis of the plane in the counterclockwisedirection. The present invention is based upon the empirical formuladiscovered, and includes the provision of means for establishing avertical, and thus determining the angle A from which can be derived theangle (AL). The means for sighting at the target is initially offsetabove the axis of the plane by the angle L and is actuated by themechanism a to generate the angle (B-L.) The ratio K between (A-L) and(B-L) is varied according to speed and altitude.

In Fig. 3 the straight edge I which is fixed to a rotatably mounted disc8, has a limiting position counterclockwise from the perpendicular tothe axis of the plane by an angle equal to the angle L. Gear teeth 9 cutin a portion of the periphery of disc 8 are meshed with the teeth of arack 10 that is slidable between guides II. The straight edge [2, whichis used for sighting at the target, is fixed to a disc l3 having teethl4 meshed with the teeth of rack l5 that is slidable in guides is, thediameter of discs 8 and I3 being equal. Link I1 is mounted on a pivot l8adjacent its lower end and has formed in it the slots l9 and 2!] the pin2|, carried by rack I being slidable in the former slot and pin 22 onrack l being slidable in the latter slot. Since the diameters of the twodiscs are the same, it follows that the angle through which straightedge I2 is turned when driven by rotation of the disc 8 is dependentupon the ratio of the distance between pivot l8 and pin 22 to thedistance between pivot I8 and pin 2|, and the link ll may be calibratedto show the position of pin 22 in slot 20 to cause the straight edge l2to pass through an angle equal to any desired fraction of the anglethrough which straight edge 1 is turned.

The straight edge I2 has an initial limiting position above the axis ofthe plane by the angle L. Therefore, when the pin 22 is set to aposition determined by the ratio factor K the angular movement of l2will be equal to (BL) when the straight edge 7 is turned through theangle (A-L), This type of sight is intended for use in a two-seaterplane. When the plane dives at an angle A the straight edge I will berotated from its initial position through a scalar angle equal to 90minus A, by the dive of the plane, and when the operator rotates thestraight edge to make it horizontal he must necessarily turn it througha scalar angle (A+L), which is a vector angle (A-L) as above defined.The pin 22 being set at the proper position for the given altitude andair speed, the straight edge i2 will be rotated by the linkage through avector angle (B-L) when the operator moves straight edge I to thehorizontal and thus will be set at the correct line of sight.

While, for purposes of illustration, the sighti log elements are shownin the form of straight edges, it is to be understood that any suitabletype of sighting device may be used in their stead.

In Fig. 4 the several parts described in Fig. 3 are given the samereference characters, but it is to be understood that Fig. 3 was largelyschematic while 4 discloses a convenient mechanical embodiment of ourinvention. Instead of having a rack which directly engages both the linkH and the disc I3, we prefer to use a rack 23 connected to the disc l3with a one-toone ratio by means of gears 24 and 25 and a shaft 26 whichmay be flexible or otherwise, as is most convenient with respect to thelocations of the several parts. The rack 23 has at one end atransversely elongated portion 21 having in it a slot 28 in which isslidable the pin 29 carried by a slide 30 mounted in a member 3| that isslidable in guides 32, the slide 30 being connected to link H by meansof pin 33 in slot 20. It will, of course, be understood that pins 29 and33 are separated by such a distance that there will be no likelihood ofthe elongated portion 21 contacting the link ll when the latter is swungon its pivot 18. The rod 34 is connected to member 31 at one end and isthreaded at its opposite end to engage the threads in the member 35 uponwhich are rotatably mounted the pinions 36 of a differential gearcarried by a frame 31. Meshed with the pinions 36 are gears 38 and 39,the gear 39 being connected to a knob 40 which is callbrated inaltitudes and the gear 39 similarly connected to a knob 4| calibrated inmiles per hour air speed. The frame 31 is fixed, and, therefore,rotation of either of the knobs 40 and 4| will cause the pinions 35 totravel around the rod 34 and thereby shift the rod lengthwise of itself,thus moving the member 3| in the slides 32. It is apparent that themovement imparted to rod 34 when the knobs 40 and 4| are simultaneouslyrotated will be the result of the algebraic sum of their rotations. Theratios between pinions 36, and pinions 38 and 39, and the pitch of thethread on rod 40 are such that the member 3| will be set to the correctposition in slides 32 to cause the desired proportional angular movementof straight edge l2 when straight edge 1 is rotated.

The mode of operation is as follows:

It having been decided from what altitude and at what air speed the bombare to be dropped,

the member 3! is set in the position corresponding to the chosen speedand altitude. After the dive has been begun the operator rotates thestraight edge 7 into parallelism with the horizon determined by sightingtransversely across it (thus eliminating the effect of dip) and hethereafter keeps it so sighted until the attack has been completed. Asabove explained, this movement oi straight edge 7 through the angle(A-L) causes the straight edge I2 to generate the angle (B-L), whichgives the correct angle B between the axis of the craft and the line ofsight to the target and angle (B-L) is varied in conformity with anychanges in the dive angle due to the fact that sightin device 1 is kepthorizontal. The pilot then directs the plane toward the target, keepingthe straight edge I2 sighted at the objective and when the chosenaltitude has been reached, the bomb is released and the plane is pulledout of the dive.

We have also provided means for adapting our invention to single seaterplanes by equipping them with the automatic control mechanism shown inFigs. 5 and 6. The gyro Wheel 42 is rotatably mounted in the ring 43which is carried on gudgeons 44 that are journalled in a cardan 45 thatin turn is pivotally mounted in a supporting bracket 46, the axis ofrotation of the gyro and the pivotal mountings of ring 43 and cardan 45being mutually perpendicular. A coil 4? is fixed on ring 43 coaxiallywith the gyro and is energized by alternating current supplied throughwires 48. A bail 49 is pivotally mounted on bracket 56 and carries twocoils 5| and 52 that are spaced from each other and normally lie inpositions that are symmetrical with respect to coil 41. The coils 5| and52 are connected to separate amplifiers carried in a case 53, the returnfrom the amplifiers to the two coils being through the common wire 54.As long as the craft is traveling horizontally, the coils 5| and 52 aresymmetrically disposed with respect to coil 4'! and have induced in themequal and opposite voltages, and therefore the outputs of the twoamplifiers annul each other and produce no torque in motor 55 whereofthe field is energized by direct current through wires and to thearmature of which the amplifiers are connected by wires 55. However,when the plane dives, the axis of spin of the gyro remains vertical andthe bail 49 being connected to the structure of the plane is moved withrespect to coil 41 which moves coils 5i and 52 from their position ofsymmetry and increases the voltage induced in one of the coils andsimultaneously weakens the volt-.

age induced in the other, with a corresponding increase in the output ofone of the amplifiers and decrease in the output of the other thereof.Since the currents supplied to motor 55 are no longer equal andopposite, a resultant torque is produced which operates the motor.Through worm 51 on the shaft of the motor and gear 58 fixed on a pivotof bail 49 and meshed with worm 51 the boil is rotated upon its pivotsand thereby turns the gear 59 which is secured on the other pivot ofbail 49 and is meshed with the rack It. The angle (11-15) is thusautomatically put into the mechanism to actuate the link i! and so causethe straight edge l2 to generate the angle (B-L).

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

We claim:

1. A dive bombing sight for aircraft, comprising a rotatably mountedsighting arm having a limiting position at an angle above a line throughthe center of rotation of said arm and parallel to the axis of the craftequal to the lift angle of the craft when in a vertical dive; a horizonarm rotatable to sight the horizon, said horizon arm having a limitingposition backward from a line perpendicular to the axis of the craftequal to the said lift angle; a first gear-toothed element connected tosaid horizon arm to rotate therewith and a second like element connectedto said sighting arm to rotate therewith, a first rack meshed with saidfirst element, a link pivoted at one end and provided adjacent theopposite end with a short longitudinal slot and with a secondlongitudinal slot extendin from adjacent said pivot past the center ofsaid link, a pin carried by said first rack extending into said shortslot, 3, pair of guides lying at right angles to said first rack and onopposite sides of said link, a member slidable in said guides, a slidecarried by said member to be movable longitudinally of said member, apin on said slide extending into said second slot, a second rack havinga slotted transversely extending portion at one end, a second pin onsaid slide disposed in the slot in said second rack, a one-to-one ratiodriving connection between said second rack and said second element, andmeans to move said member to a position in said guides determined by afunction of a chosen altitude and the air speed of the craft.

2. A dive bombing sight for aircraft, comprising a sighting devicemounted for rotation in the vertical plane of its longitudinal axis, andhaving a limiting position somewhat above a line parallel to the axis ofthe craft, a horizon sighting device mounted for like movement andhaving a limiting position slightly back of the perpendicular to theaxis of the craft, means connecting said two devices whereby movement ofthe latter moves the former, said means including an adjustable ratiolinkage to cause the angular movement imparted to said sighting devicefrom said horizon sighting device to be a predetermined proportion ofthe angular movement of said horizon sighting device, and in the sameangular sense, and means to adjust said linkage to operate roportionallyto a function of a predetermined air speed and also to a function of apredetermined altitude.

3. A dive bombing sight for aircraft, comprising a sighting devicemounted for rotation in the vertical plane of its longitudinal axis, andhaving a limiting position somewhat above a line parallel to the axis ofthe craft, a horizon sight ing device mounted for like movement andhaving a limiting position slightly back of the perpendicular to theaxis of the craft, means conmeeting said two devices whereby movement ofthe latter moves the former, said means including an adjustable ratiolinkage to cause the angular movement imparted to said sighting devicefrom said horizon sighting device to be a predetermined proportion ofthe angular movement of said horizon sighting device and in the sameangular sense, and means including a differential gear to adjust saidlinkage to operate proportionally to a function of a predetermined airspeed and also to afunction of a predetermined altitude.

4. A dive bombing sight, comprising a first sighting device angularlymovable in a vertical plane for sighting a target, a second sightingdevice likewise movable for sighting the horizon, the first said devicehaving a limiting position offset 'above a line parallel to the axis ofthe craft by an angle equal to the lift angle of the craft when in avertical dive, and the second said device being offset back of thevertical to said axis by an equal angle, and an adjustable ratio linkageoperatively connecting the said devices, said linkage being settable tooperate in accordance with a function of a predetermined air speed and afunction of a predetermined altitude.

5. A dive bombing sight, comprising a first sighting device angularlymovable in a vertical plane for sighting a target, a second sightingdevice likewise movable in said plane for sighting the horizon, and anadjustable ratio linkage operatively connecting the said devices, saidlinkage being settable to operate in accordance with a function of apredetermined air speed and a function of a predetermined altitude.

6. A dive bombing sight, comprising a sighting device angularly movablein a vertical plane for sighting a target, an adjustable ratio linkageoperatively connected to said device, means to set said linkage to causethe movement imparted to said device to be a function of a predeterminedair speed and also a function of a predetermined altitude, andgyroscopically controlled means to impart to said sighting devicethrough said linkage a movement that is a function of the angle ofinclination of the axis of the craft to the vertical.

'7. A dive bombing sight, comprising a sighting device angularly movablein a vertical plane for sighting a target, an adjustable ratio linkageoperatively connected to said device, means to set said linkage to causethe movement imparted to said device to be a function of a predeterminedaltitude, and stabilized means to impart to said sighting device throughsaid linkage a movement that is a function of the angle of inclinationof the axis of the craft to the vertical.

8. A dive bombing sight, comprising a sighting device angularly movablein a vertical plane for sighting a target, an adjustable ratio linkageoperatively connected to said device, means to set said linkage to causethe movement imparted to said device to be a function of a predeterminedair speed and also a function of a predetermined altitude, and automaticmeans to impart to said sighting device through said linkage a movementthat is a function of the angle of inclination of the axis of the craftto the vertical.

9. A dive bombing sight, comprising a first sighting device angularlymovable in a vertical plane for sighting a target, a second sightinglikewise movable for sighting the horizon, means interconnecting saiddevices to move said first sighting device through an angle equal to theangle between the axis of the craft and the correct line of sight to atarget plus the lift angle of the craft in a vertical dive while thesecond sighting device is moved through an angle that is equal to theangle of inclination of the axis of the craft to the vertical plus thesaid lift angle, the said means being adjustable to vary in accordancewith a function of a chosen air speed and a chosen altitude the anglethrough which the first said device is moved.

10. A dive bombing sight, comprising a sighting device for sighting atarget, gyroscopically controlled means to move said device through anangle equal to the angle between the axis of the craft and the correctline of sight to a target plus the lift angle of the craft when in avertical dive, and means to adjust the first mentioned means to vary inaccordance with a function of a chosen air speed and a chosen altitudethe angle through which said sighting device is moved.

11. A dive bombing sight, comprising a sighting device for sighting atarget, stabilized means to move said device through an angle equal tothe angle between the axis of the craft and the correct line of sight toa target plus the lift angle of the craft when in a vertical dive, andmeans to adjust the first mentioned means to vary in accordance with afunction of a chosen air speed and a chosen altitude the angle throughwhich said sighting device is moved.

12. A dive bombing sight, comprising a sighting device for sighting atarget, automatic means to move said device through an angle equal tothe angle between the axis of the craft and the correct line of sight toa target plus the lift angle of the craft when in a vertical dive, andmeans to adjust the first mentioned means to vary in accordance with afunction of a chosen air speed and a chosen altitude the angle throughwhich said sighting device is moved.

13. Dive bomb sighting means comprising a straight edge sighting memberadapted to be maintained with its length parallel to the horizon, asecond sighting member for sighting at a target, adjustable linkagemeans connecting said sighting members, and means to change the ratio ofsaid linkage proportionately to a function of an air speed and analtitude.

MAURICE E. BROWDER. ALBERT WERTHEIMER.

